Pneumatic level control

ABSTRACT

A pneumatic level control system for controlling the level of a flowable substance in a contained area. The system comprises a level control means having a first pneumatic level sensing means. Switching means are associated with the first level sensing means and operable by a first predetermined pressure in the first level sensing means to operate a transporting device connected to the contained area for transferring the substance. A second pneumatic level sensing means prevents the first predetermined pressure from building up in the first pneumatic level sensing means until the level of the substance reaches a further predetermined level.

United States Patent 1191 Hewlings 51 Nov. 27, 1973 PNEUMATIC LEVELCONTROL [76] Inventor: Winston G. Hewlings, Montreal, :nmary fg g gFreeh [22] F1led: May 3, 1972 [57] ABSTRACT [21] Appl' 249917 Apneumatic level control system for controlling the level of a flowablesubstance in a contained area. The [52] US. Cl. 417/36, 417/44 systemcomprises a level control means having a first [51] Int. Cl. F04b 49/02,F04b 49/06 pneumatic level sensing means. Switching means are [58] Fieldof Search 417/36, 44 associated with the first level sensing means andoperable by a first predetermined pressure in the first level [56]References Cited sensing means to operate a transporting device con-UNITED STATES PATENTS nected to the contained area for transferring thesubstance. A second pneumatic level sensing means preilfi $1133?221112211113"'""""3311:1313171577184 the free predetermined freerbuilders 3:431:858 3/1969 Lynn 417 36 x P in the first Pneumetic levelSensing means until the 3,021,789 2/1962 Ryden 417/36 level of theSubstance reaches a further predetermined 3,360,002 12/1967 Weis 137/395level.

3,393,642 7/1968 Kordik .l 417/36 3,424,090 1 1969 Hyde 417 44 x 4Claimsr 1 Figure 1 PNEUMATIC LEVEL CONTROL BACKGROUND OF INVENTION 1.Field of the Invention The present invention relates to a pneumaticlevel control system for controlling the level of a flowing substancebeing introduced into a containing area.

2. Description of Prior Art Many of the level control apparatuspresently used to control the operation of a pump to maintainpredetermined levels of liquid in a containing area, such as a sump wellfor sewage sump application, utilize float mechanisms connected toshut-off valves or electrical contacts to start and stop an associatedfluid pump connected to the well. These types of control have manydisadvantages in that they are difficult to install or ser* vice, notvery reliable because their operating components are subject tocorrosion by the liquids in which they rest and their linkages becomejammed by sewage or impurities in the liquid. Further, these are veryunsanitary when requiring repair or installation.

SUMMARY OF INVENTION It is a feature of the present invention to providea pneumatic level control which substantially overcomes theseabove-mentioned disadvantages and which is economical to produce.

According to this feature, from a broad aspect, the present inventionprovides a pneumatic level control system for controlling the level offlowable substance in a contained area. The system comprises a levelcontrol means having a first pneumatic level sensing means. Switchingmeans are associated with the first level sensing means and operable bya first predetermined pressure in the first level sensing means tooperate a transporting device connected to the contained area fortransferring the substance.

BRIEF DESCRIPTION OF DRAWING A preferred embodiment of the presentinvention will now be described with reference to the accompanyingdrawing which is a schematic representation of the pneumaticlevelcontrol system of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawing, thereis shown a contained area in the form of a sump or well being fed withliquid substance 11 from a sewer discharge pipe opening 12. The sump orwell 10 can be fed by any other suitable means located suitably relativeto the contained area. A substance transporting device herein shown as aliquid pump 25 is provided with an intake pipe 13, of which the intakeopening 14 is positioned a predetermined distance above the bottomsurface 15 of the well 10. The pump 25 is turned on" and off bylevel'control means 16 whereby the well 10 will not overflow into thesewer discharge pipe and will periodically discharge from a secondpredetermined level L to a first predetermined level L L is thepredetermined lower level or stop level for the liquid in the well 10.

The level control means 16 comprises a first pneumatic level sensingmeans, herein shown as a hollow elongated conduit or pipe 17 extendingpartly down the well 10 below the discharge pipe opening 12. A secondpneumatic level sensing means, also in the form of a hollow conduit orpipe 18, but shorter than pipe 17 by a predetermined distance d, alsoextends down the well below the discharge pipe opening 12. An air pump19 is connected to the end of the level sensing pipe 17 outside the well10 and pumps air down the pipe 17 in the direction of arrow 27. Apressure sensing device 20 incorporating a differential switch 24, isconveniently connected to the pipe 17 via a T-coupling 21 locatedbetween the pump 19 and the liquid 11 in the well. An adjustable valve22 connects the second level sensing pipe 18 to the pipe 17 via afurther T-coupling 23 located in pipe 17 downstream from the air switch20.

It is possible to provide a level control system with the first levelsensing pipe 17, only.

The pressure sensing device 20 has a sensing diaphragm (not shown) whichis adjustable and operates by predetermined pressures in the pipe 17.The air switch 20 also incorporates a differential switch 24. Thisparticular switch 24 requires approximately twice as much pressure tooperate than to release. When the sensing device 20 is operated, itcauses an associated switch 24 to activate the pump 25. With valve 22closed, when the liquid level inside the well 10 rises above the stoplevel L,, the pressure builds up and at level L sufficient pressure ispresent in the pipe 17 to cause the switch 24 to operate and the pump 25would start. However, due to the differential feature contained in theswitch 24 it would not reset until the level returns to L,. Theadvantage of the delay to operate the differential switch 24 is that itprevents the pump 25 from being switched on and off momentarily andfrequently, as the level of liquid increases very slightly above thestop level L,. As the level of liquid 11 drops to the stop level L theswitch 24 is released, stopping the pump 25. As mentioned hereinabove,the reason why the switch 24 does not release immediately as the liquidlevel drops below level L; is that only half of the switch operatingpressure is required to release the switch 24. Thus, the system mayoperate with the first level sensing means (level sensing pipe 17).

In the second and preferred application of the system utilizing pipes 17and 18, when the valve 22 is open, some of the air being fed down thepipe 17 will bleed through the valve 22 and down pipe 18, in thedirection of arrow 28, especially as the liquid level increases abovethe lower end 30 of pipe 17. Thus, as the liquid level continues torise, air continues to bleed through the lower end 31 of pipe 18 andpressure does not build up in pipe 17 in the area of air switch 20 untilthe liquid level reaches the lower end 31 of pipe 18 and continues torise until it reaches a predetermined start level L where the pressurein the pipe 18 and also 17, via valve 22, has reached the pressuresufficient to operate the sensing device 20, which in turn activates theswitch 24 and turns the fluid pump 25 on. The start level L, or startpressure is adjustable by the valve 22 by adjusting the size of itsconnecting orifice. When the liquid level decreases, to thepredetermined stop level L the pressure in the pipe 17 has dropped tothe predetermined pressure which turns off the fluid pump 25.

With the arrangement of level sensing pipes 17 and 18, it can be seenthat the level control means can be easily adapted to wells of anydepths. Also, the level difference D" of liquid required to activate thefluid pump 25 can be adjusted by simply varying the distance d," thatis, the distance between the ends of pipes 17 and 18. Consequently, thedistance D is adjustable.

It is within the ambit of the present invention to utilize theabove-described level control system for applications other than thepreferred one described herein. For example, the system could be used tocontrol the level of a flowable substance such as a powder.

I claim:

1. A pneumatic level control system for controlling the level of aflowable substance in a contained area, said system comprising levelcontrol means having a first pneumatic level sensing conduit having oneend extending below a predetermined lower level of substance in saidcontained area, a second pneumatic level sensing conduit connected tosaid first sensing conduit through an adjustable valve and having an endpositioned above said lower level of substance below a secondpredetermined level, said second predetermined level being controlled bysaid adjustable valve, switching means connected to said first sensingconduit and operable by a first predetermined pressure in said firstconduit after the level of substance has risen to said secondpredetermined level, said switching means controlling the operation of asubstance transporting device connected to said contained area fortransfening said substance, said switching means being released when thepressure in said first conduit reaches a second predetermined pressurewhich is lower than said first predetermined pressure.

2. A pneumatic level control system as defined in claim I, wherein saidfirst level sensing conduit has its other end connected to an air pumpfor pumping air down said first conduit for release under said lowerlevel of said substance.

3. A pneumatic level control system as claimed in claim 1, wherein saidswitching means incorporates a differential air switch which isconnected to control the operation of said transporting device, saidtransporting device being a pump connected to said contained area fortransferring said substance.

4. A pneumatic level control system as claimed in claim 3, wherein saiddifferential switch is operable by said first predetermined pressurewhich is approximately twice the force as said second predeterminedpressure whereby said differential switch is released and said liquidpump is shut off.

1. A pneumatic level control system for controlling the level of aflowable substance in a contained area, said system comprising levelcontrol means having a first pneumatic level sensing conduit having oneend extending below a predetermined lower level of substance in saidcontained area, a second pneumatic level sensing conduit connected tosaid first sensing conduit through an adjustable valve and having an endpositioned above said lower level of substance below a secondpredetermined level, said second predetermined level being controlled bysaid adjustable valve, switching means connected to said first sensingconduit and operable by a first predetermined pressure in said firstconduit after the level of substance has risen to said secondpredetermined level, said switching means controlling the operation of asubstance transporting device connected to said contained area fortransferring said substance, said switching means being released whenthe pressure in said first conduit reaches a second predeterminedpressure which is lower than said first predetermined pressure.
 2. Apneumatic level control system as defined in claim 1, wherein said firstlevel sensing conduit has its other end connected to an air pump forpumping air down said first conduit for release under said lower levelof said substance.
 3. A pneumatic level control system as claimed inclaim 1, wherein said switching means incorporates a differential airswitch which is connected to control the operation of said transportingdevice, said transporting device being a pump connected to saidcontained area for transferring said substance.
 4. A pneumatic levelcontrol system as claimed in claim 3, wherein said differential switchis operable by said first predetermined pressure which is approximatelytwice the force as said second predetermined pressure whereby saiddifferential switch is released and said liquid pump is shut off.